A textbook is an organized body of material useful for the formal study of a subject area. A good textbook is distinguished by:

A discrete, well-bounded scope: all the material should relate to a solid understanding of the subject, usually mixing theory and practice for each topic as it covers the subject domain.

Use of examples and problems: the student should be able to better grasp each presented concept by following examples, and then applying the concept in structured exercises or problems.

An internally consistent style: after the first few sections, there should be little or no surprises for the student in terms of layout and presentation of material. The text's user can get comfortable with the layout, the tempo of presentation, and the pattern of figures, illustrations, examples and exercises.

Utility for future reference: once reviewed, the textbook should isolate material that is useful to the future application of subject knowledge in well organized appendices and tables.

A structure that makes sense: the textbook is not just a collection of useful material, it is a guide to the student for an order of review which will aid in mastering the subject area.

Topics are presented in major parts, chapters, sections and subsections that ore organized in a way that facilitates understanding. This means that the text's organization is based on the intersection of two requirements. The first of these are the requirements of the subject domain. Since most textbooks are developed by, or based on the contributions of subject matter experts, this requirement is usually well attended to.

The second requirement is defined by the limits of the student's mind. Cognition is a common human ability, but its needs and limits are frequently ignored by those who have already mastered a subject area. To make the best use of the student's abilities, some rules can be spelled out for the structuring and presentation of ideas, concepts, and material. These rule should include:

Rule of Frameworks: Memory and understanding are promoted by the use of a structure that mimics the structures we all use within our minds to store information. Before we can use or master a subject, we have to have a mental roadmap that allows us to navigate within and through the subject domain. The text can best aid understanding by making this framework visible early on within each section or topic. The extent to which the student understands that they are using a framework, and knows what that framework is, is important as they internalize and make use of the material presented.

Rule of Meaningful Names: Everything we know is tagged with an index or a title. These indices are critical to the ability to recall or retrieve the things we know and remember. Each concept, process, technique or fact presented should aid the student to assign a meaningful name for it in their own mental organization of the material. To be most useful, these names shouldn't have to be relearned at higher levels of study. The names assigned by the text should be useful in that they support some future activities: communication with other practitioners, reference within the text to earlier mastered material, and conformity to the framework used for the subject. Each unique element of the subject domain should have a unique name, and each name should be used for only one element.

Rule of Manageable Numbers: When we learn from an outline, an illustration, or an example; most of us are limited in our ability to absorb new material. As we become familiar with part of a subject domain this number expands, but for new material four to six new elements is a reasonable limit. If a chapter outline contains 12 items, the student will have forgotten the outline before getting to the last item. When a text fails to support this rule, it requires even a diligent student to needlessly repeat material.

Rule of Hierarchy: Our mental frameworks are hierarchical. Learning is aided by using the student's ability to couple or link new material with that already mastered. When presenting new domains for hierarchical understanding, the rules for meaningful names and manageable numbers have increased importance and more limited application. A maximum of three levels of hierarchy should be presented at one time. The root should be already mastered, the current element under consideration clearly examined, and lower levels outlined only to the extent that they help the student understand the scope or importance of the current element. This area is supplemented by two more rules within this rule: thoseof Connectivity and Cohesion. Connectivity requires consideration of what the student likely knows at this point. The more already mastered elements that one can connect with a new element, the easier it is to retain. Cohesion requires that the characteristics of new elements as they are presented be tightly coupled.

Rule of Repetition: Most people learn by repetition, and only a few with native genius can achieve mastery without it. There is a pattern of repetition that aids in promoting the elements of a subject from short-term to long-term memory. Implementations of this rule may mean that frameworks and important hierarchies are repeated as many as five or six times, while frequently used elements are repeated three or four times, and elements of lesser utility may not be repeated at all. The first repetition should normally occur within a day of first presentation, followed by a gradually decreasing frequency. Exercises and review sections are ideally contribute a designed repetition pattern.